Refrigerating compressor with oil cooler



United States Patent O 3,548,612 REFRIGERATING COMPRESSOR WITH OILCOOLER Mamoru Mitsubayashi, Yasuhiko Muraishi and Kazuichi Nishitsuji,Numazu-shi, Shizuoka-ken, Japan, assignors, by mesne assignments, toTokyo Shibaura Denki Kabushiki Kaisha, also known as Tokyo ShibauraElectric Co., Ltd., Kawasaki-shi, Kan-agawa-ken, Japan, a jointstockcompany of Japan Filed Jan. 27, 1969, Ser. No. 794,096 Int. Cl. F25!)43/02 US. Cl. 62469 3 Claims ABSTRACT OF THE DISCLOSURE In ahermetically sealed type compressor, an oil cooler is provided to coolthe lubricant contained in a casing which encloses the compressor, and aportion of a liquid refrigerant is circulated through the oil coolerfrom the condenser to cool the lubricant and compressor. In a modifiedembodiment an ejector is connected between the compressor and condenserto enhance circulation of the refrigerant through the oil cooler.

BACKGROUND OF THE INVENTION This invention relates to refrigeratingapparatus and more particularly to an improved device for preventingoverheating of hermetically enclosed type refrigerant compressors.

A recent trend in refrigerating apparatus requires compressors of smallsize, light weight and high efficiency. To meet these requirements,compressor driving motors have been changed from four-pole to two-poletype to double their speed and to decrease piston displacement percylinder thus decreasing their physical size. In compressors driven byfour-pole motors, temperature rise during operation of the refrigeratoris not excessive because the speed of motors and compressors isrelatively low, and, hence, the quantity of heat generated thereby issmall, and because the motor compressors are relatively massive and,hence, have a large heat dissipating surface. However, in high-speedcompressors driven by two-pole type motors, as the quality of heatgenerated is increased and as their physical size is greatly reduced,the temperature rise of the compressors is much higher than that ofcompressors driven by four-pole type motors, so that under certainoperating conditions, they are overheated, thus causing defectiveoperation of failure. Especially in compressors used in low-temperaturerefrigerating apparatus operating at temperatures as low as 40 C. orlower, the temperature of the compressors rises excessively due to therelatively small quantity of gaseous refrigerant circulating through therefrigerating system and high compression ratio of the refrigerant, thusgiving rise to such trouble as decrease in the compressor efficiency,deterioration of the lubricating oil for the compressors, which in turncauses seizure of bearings, damage to valves, burning out of drivingmotors, etc.

A conventional motor-driven compressor is sealed in a casing, and themotor-compressor assembly is resiliently supported in the casing byspring means. A quantity of lubricant is contained in the bottom of thecasing to lubricate rotary parts of the motor and compressor. Usually aheat exchanger or an oil cooler is provided in the body of thelubricant. Cooling water is circulated through the oil cooler inparallel with a condenser for the compressed refrigerant wherebyoverheating of the compressor is prevented. The cooling effect of theoil cooler, however, gradually decreases due to accumulation of scaletherein. In household refrigerators, as the overall size of the motorcompressor has been decreased by the adoption of high-speed machines,the size of the oil cooler is also limited. For this reason, a smallaccumulation of scale greatly reduces the cooling effect, thus causingoverheating. When the refrigerator is not used, as in winter, thecooling water remaining in the oil cooler often freezes to break the oilcooler. To prevent this, it is usually to provide a drain cock for theoil cooler. However, as the oil cooler is disposed in the bottom of thecompressor casing, such a drain cock must be positioned beneath thecompressor casing, which requires difficult work. Even when such a draincock is provided the user may often forget to operate the drain cock.

SUMMARY OF THE INVENTION It is therefore an object of this invention toprovide a new and improved refrigerating apparatus in which the abovementioned defects are eliminated.

Another object of this invention is to provide a novel refrigeratorwherein the lubricant for a motor-driven compressor contained in asealed casing is cooled by the evaporation of a portion of the liquifiedrefrigerant.

Still another object of this invention is to provide an improvedlubricant cooler for a sealed type compressor including means to createforced circulation of the liquid refrigerant through the lubricantcooler.

According to this invention a portion of the liquid refrigerantcondensed in the condenser is caused to circulate through the oil coolercontained in a sealed casing accommodating a motor compressor. Accordingto a modified embodiment of this invention, an ejector is included in aconduit between the compressor and the condenser to induce forcedcirculation of the refrigerant through the oil cooler. Where thequantity of refrigerant circulating through the refrigerating system issmall, as in the case of low temperature operation, the ejector ispositioned at substantially the same level as the oil cooler to enhancecirculation of the refrigerant through the oil cooler. In this case acapillary tube is connected in parallel with the ejector to prevent backflow of the liquid refrigerant to the compressor.

BRIEF DESCRIPTION OF THE DRAWING The invention can be more fullyunderstood from the following description taken in conjunction with theaccompanying drawing in which:

FIG. 1 is an elevation, in vertical section, of a sealed type motorcompressor provided with an oil cooler;

FIGS. 2, 3 and 4 are diagrams of three different embodiments of thisinvention; and

FIG. 5 is a longitudinal section of an ejector utilized in theembodiments shown in FIGS. 3 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1 whichshows a vertical section of a sealed type motor compressor 1 forhousehold refrigerators. A compressor 20 and its driving motor 21 areresiliently supported in a hermetically sealed casing 18 by means ofsuitable supporting springs 19 (only one is shown). To lubricatebearings, cylinders and other sliding parts 22, a quantity oflubricating oil 23 is contained in the bottom of casing 18, and an oilcooler 8 in the form of a spiral coil is immersed in lubricating oil 23.

As diagrammatically shown in FIG. 2, a high-temperature, high-pressuregaseous refrigerant compressed by motor compressor 1 is conveyed to acondenser 3 via a conduit 2. Condenser 3 is cooled by suitable meanssuch as a water cooled coil 9. Condensed refrigerant then passes to anevaporator 6 via a conduit 4 and a through or expansion valve 5. Gaseousrefrigerant generated in the evaporator then passes to motor compressor1 and Dec. 22, 1970 MAMQRU WTSUBAYASHI ET AL 3,54%,632

REFRIGERATING COMPRESSOR WITH OIL COOLER Filed Jan. 27', 1969 MAMORUMITSUBAYASHI, YASUHIKO MURAISHI and KAZUICHI NISHITSUJI,

INVENTORS ATTORNEY

